A brief report on ichthyofaunal diversity of Dewmai khola of Ilam district, Nepal

Fish diversity of Nepal has been poorly studied or understood relative to other fauna, so a lot of study is still required to have a better fish diversity profile. We investigated ichthyofaunal diversity on one of the unexplored rivers, Dewmai Khola which lies in mid-hill region of Ilam district in eastern Nepal. Fishes were collected from three sampling sites in day time by using a cast net with the help of local fisherman. The field visits were performed from December2015 to September 2016. A total of 16 fish species belonging to 3 orders, 6 families and 11genera have been recorded. The Cypriniformes was the dominant order represented by 3families: 1) Cyprinidae with 7 species (Cirrhinus mrigala, Barilius barila, B. bendelisis, Bengalaelanga, Danio aequipinnatus, Schizothoraichthys labiatus and Garra gotyla), 2) Cobitidae with5 species (Schistura multifasciatus, S. horai, S. scaturigina, S. savona and S. rupecula) and3) Psilorhynchidae with a single species Psilorhynchus pseudecheneis. The Perciformes was represented by two families with a single species in each: Belontidae (Colisa fasciatus) and Channidae (Channa stewartii). The Siluriformes was represented by a single family Sisoridae with a single species Glyptothorax pectinopterus.

Using collision cones to assess biological deconfliction methods

Biological systems consistently outperform autonomous systems governed by engineered algorithms in their ability to reactively avoid collisions. To better understand this discrepancy, a collision avoidance algorithm was applied to frames of digitized video trajectory data from bats, swallows and fish ( Myotis velifer , Petrochelidon pyrrhonota and Danio aequipinnatus ). Information available from visual cues, specifically relative position and velocity, was provided to the algorithm which used this information to define collision cones that allowed the algorithm to find a safe velocity requiring minimal deviation from the original velocity. The subset of obstacles provided to the algorithm was determined by the animal's sensing range in terms of metric and topological distance. The algorithmic calculated velocities showed good agreement with observed biological velocities, indicating that the algorithm was an informative basis for comparison with the three species and could potentially be improved for engineered applications with further study.

Sensitivity of cones from a cyprinid fish (Danio aequipinnatus) to ultraviolet and visible light

Photocurrents of cones in the retinas of a small fish, Danio aequipinnatus (Cyprinidae) were recorded with suction pipette electrodes. Spectral sensitivity was measured between 277 and 697 nm. Four spectral classes of cone were found, with λmax at 560, 480, 408, and 358 nm. For the latter, we provide the first complete characterization of spectral sensitivity of a vertebrate ultraviolet (UV) photoreceptor. All cones responded with similar kinetics, except for a subset of the 560-nm cones, which were distinctly faster. The a-bands of the three cones absorbing maximally in the visible have the same bandwidth when log sensitivity is plotted versus normalized frequency, and in this respect they are indistinguishable from primate cones (“Mansfield's rule’). An eighth-degree polynomial in λmax/λ based on this combined data set (fish, primate) is presented as a template that is likely to have predictive value in describing cone spectra from other vertebrates. The α−band of the UV cone, however, is somewhat narrower than predicted by this function, is similar to other UV visual pigments, and an eighth-degree polynomial that describes its shape is also presented. These measurements also provide information on the β−band (i.e. cis peak region), difficult to obtain by microspectrophotometry. The β−band of cone pigments is found at longer wavelengths as the α−band shifts toward the red. A secondary rise in cone sensitivity around 280 nm indicates that photons absorbed by aromatic amino acids in the opsin (γ−band) excite the transduction cascade, but the quantum efficiency is not as high as when absorption occurs in the retinal-protein chromophore.